Much of the minute abrasive alloy particles produced by wear in engines or other machine apparatus are removed from the immediate site of production by lubrication oil only to be reintroduced as the lubrication fluid is recycled and reapplied onto the site. Most often the lubrication fluid is filtered through a paper, fiber or equivalent filter, such as disposable screw-on canister filters, before being recycled through the lubrication system. However, economically feasible or practical filters have little or no effectiveness for the smaller particles, especially minute abrasive metal particles. Providing a filter or filter system with sufficiently fine filtration would be excessively costly and/or excessively impede the fluid flow, and thus be unacceptable for the majority of the applications.
Attempts to enhance the filtration of canister type filters include simple magnets applied to a single point or area on or about the canister. However, the previously known structures typically provide limited or incomplete magnetic paths and/or produce a magnetic field over an ineffectively small region of the canister filter, producing disappointing and unusable results.